Cook the Spinach

In a skillet over medium heat melt the butter. Add onion and cook for a few minutes, stirring frequently, until the onions become slightly translucent. Add the minced garlic and cook about 30 seconds, stirring constantly. Add the chopped spinach, thyme, sage and parsley. Add a pinch of salt, stirring to incorporate. Add ¼ cup water and cook uncovered until spinach has wilted and the liquid has evaporated.

Make the Custard

In a large bowl combine the eggs, milk, heavy cream, salt and black pepper. Whisk until well combined. Set aside.

Assemble the Strata

Tear your croissants into chunks. 

Grease a 9×13 baking dish with the 1 tablespoon of butter.  Spread ⅓ of the croissant chunks across the bottom of the pan. Top with ⅓ of the spinach mixture and ⅓ of the cheeses. Make sure you spread out the spinach mixture. Repeat until you have used up all the croissant chunks, spinach and cheeses.

Pour the custard over the croissant layers. Cover with plastic wrap and let the croissants soak up the liquid. Place in the fridge and let the strata chill for at least 1 hour and up to overnight. (I usually let it sit on the counter for an hour and then place it right in the oven to reduce the cooking time.)

Bake the Strata

Heat oven to 350F.  Remove the plastic wrap.

If your strata was sitting on the counter: Bake the strata covered with aluminum foil for 20 minutes. Then uncover and continue cooking for 30-40 minutes more, or until the custard is set and the strata is golden on top. 

If your strata was chilling in the fridge: Bake the strata covered with aluminum foil for 30 minutes. Then uncover and continue cooking for 40-45 minutes more, or until the custard is set and the strata is golden on top.  

In either case, check oven towards the end of the baking time to make sure your strata does not overcook. 

Let the strata rest for 15 minutes before serving. This will help it hold together when you get into it and also helps avoid burnt mouths.